This invention relates to an energy management system and method for absorbing and directing kinetic energy during an impact event of a motor vehicle. More particularly, the present invention relates to a deformable aluminum attachment bracket for attaching an extruded vehicle subframe to a vehicle chassis, where the attachment bracket is purposely deformed upon experiencing an impact load above a predetermined level, allowing the subframe to drop down and below the vehicle chassis during an impact event.
The controlled management of kinetic energy remains a primary consideration in the design of motor vehicle structures to reduce the likelihood and severity of injury to vehicle occupants in the event of a collision. An aspect of such management is to minimize the effect of the so-called xe2x80x9csecondary collisionxe2x80x9d that occurs between a vehicle occupant and the vehicle interior when the vehicle""s occupant compartment is suddenly de-accelerated relative to the occupant. Another aspect is the reduction of intrusions of vehicle components and structures, such as the engine and transmission, into the occupant compartment during the impact event. While significant advances have been made in this regard, including two and three-point seat belt systems, instrument panel padding and knee bolsters, airbags, energy absorbing steering columns, non-invasive brake and accelerator pedals, reinforced occupant compartment structures, and energy absorbing deformable body panels and frames, efforts continue to further improve the state of the art in vehicle occupant restraint and protection.
One example of an energy absorbing structure is found in U.S. Pat. No. 3,171,669, where intermediate connecting members are inserted between the longitudinal bearer members of the vehicle and an impact-protective device, for instance, a bumper, at the vehicle front and rear. The structure disclosed therein exhibits a resistance against impact decreasing in the direction from the wheel axes toward the vehicle rear or front for reducing the impact forces transmitted to the frame or main central vehicle frame structure. Impact resistance is partially obtained through breakable bolts securing the vehicle grill to the vehicle structure. In U.S. Pat. No. 6,022,057, energy absorption is obtained by fixing a construction, such as a front brush bar, to the front of a vehicle, where the construction absorbs energy during a collision. The construction is disclosed as being attached to the vehicle via coupling elements having a weakened (i.e., buckled) portion that is deformable. However, in neither design is there provision for minimizing component stackup, while also maximizing dynamic crash performance during the initial crash event while also reducing component intrusion into the occupant compartment.
Moreover, traditional subframe bolt shearing as an energy absorbing structure has been found impractical in certain applications, particularly with the trend toward lightweight vehicle structural materials, such as aluminum. An example of such an application is found in U.S. Pat. No. 5,085,485, where vehicle body structures are formed by extruded sections manufactured of aluminum. Relatively high-energy absorption is obtained by the use of a member having a central tube portion and two outer hollow-sections connected to the tube portions. But the use of shearing steel bolts in such application is nearly impossible when used in conjunction with relatively softer and less stiff structures, such as aluminum, that are becoming more and more prevalent in vehicle structures. For example, a pair of M12 PC 8.8/10.9 bolts, having a nominal axial ultimate strength of 31,000/40,000 lbs. of force, requires a shearing load of about 23,000/30,000 lbs., applying a 1.3 shear factor. However, such a load will collapse the typical overall aluminum structural assembly prior to any shearing of the bolts. Thus, where the longitudinal load members are manufactured from aluminum to carry and transfer load to the main vehicle support structure, the shear load level obtained with traditional shear bolts as used with steel structures is simply too high to render shearing of the bolts feasible.
According to the present invention, an energy management system and method for absorbing and directing vehicle kinetic energy during a frontal impact event of a motor vehicle includes an extruded vehicle subframe extending longitudinally from a vehicle chassis, where a pair of deformable attachment brackets are interposed between the vehicle chassis and subframe along each lateral side of the vehicle. The deformable attachment brackets, preferably fabricated from aluminum, attach the subframe to the vehicle chassis, where the deformable attachment brackets are preferably fixedly attached to the subframe and removably attached to the vehicle chassis via fasteners extending through a fastener hole in each of the attachment brackets.
A relief opening is provided proximate to and aligned with the fastener hole, the size of the relief opening being larger than the outer diameter of the fastener. A deformable barrier is disposed between the fastener hole and relief opening, with the barrier preferably provided with a slot extending between the fastener hole and relief opening. The subframe is formed from a set of interconnected extruded rails having a front cross-member and a forwardly extending front rail attached to a transverse beam, wherein each of the front cross-members and forwardly extending front rails are fixedly attached to the deformable attachment bracket.
Upon a vehicle impact generating an impact force on the transverse beam above a predetermined force, the fastener deforms the deformable barrier and is displaced longitudinally from the fastener hole into the relief opening. The deformable attachment bracket, and the attached subframe, drop down beneath the vehicle chassis during the impact event, with the subframe then free to translate longitudinally relative the vehicle chassis during the crash event, safely away from the vehicle occupant compartment.
The above brief description sets forth rather broadly the more important features of the present disclosure so that the detailed description that follows may be better understood and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the disclosure that will be described hereinafter which will form the subject matter of the claims appended hereto.
In this respect, before explaining the preferred embodiment of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the following description or drawings. The energy management system and method for absorbing and directing vehicle kinetic energy during a frontal impact event of a motor vehicle of the present disclosure is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation. Where specific dimensional material specifications have been included or omitted from the specification of the claims, or both, it is to be understood that the same are not to be incorporated into the appended claims.
As such, those skilled in the art will appreciate the conception, upon which this disclosure is based, may readily be used as a basis for designing other structures, methods and systems for carrying out the purposes of the present invention. It is important therefore that the claims are regarded as including such equivalent instructions as far as they do not depart from the spirit and scope of the present invention.
Further, the purpose of the Abstract is to enable the U.S. Patent and Trademark Office and the public generally, especially the scientists, engineers and practitioners in the art who are not familiar with the patent or legal phraseology, to learn quickly from a cursory inspection the nature and essence of the technical disclosure of the application. Accordingly, the Abstract is intended to define neither the invention nor the application, which is only measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.